curcumin and Facial-Pain

Curcumin has diverse therapeutic effects, such as anti-inflammatory, anti-oxidant, anti-cancer, and antimicrobial activities. The vanilloid moiety of curcumin is considered important for activation of the transient receptor potential vanilloid 1 (TRPV1), which plays an important role in nociception. However, very little is known about the effects of curcumin on nociception. In the present study, we investigated whether the anti-nociceptive effects of curcumin are mediated via TRPV1 by using nociceptive behavioral studies and in vitro whole-cell patch-clamp recordings in the trigeminal system. Subcutaneous injection of capsaicin in the vibrissa pad area of rats induced thermal hyperalgesia. Intraperitoneally administered curcumin blocked capsaicin-induced thermal hyperalgesia in a dose-dependent manner. Whereas curcumin reduced capsaicin-induced currents in a dose-dependent manner in both trigeminal ganglion neurons and TRPV1-expressing HEK 293 cells, curcumin did not affect heat-induced TRPV1 currents. Taken together, our results indicate that curcumin blocks capsaicin-induced TRPV1 activation and thereby inhibits TRPV1-mediated pain hypersensitivity.

Topics: Animals; Capsaicin; Cell Line; Curcumin; Facial Pain; Hot Temperature; Humans; Hyperalgesia; Injections, Intraperitoneal; Injections, Subcutaneous; Kidney; Male; Nociceptors; Nose; Patch-Clamp Techniques; Rats; Rats, Sprague-Dawley; Trigeminal Ganglion; TRPV Cation Channels

The present study was planned to evaluate the role of curcumin in the formalin-induced orofacial pain in rats that mimics typical human orofacial pain. Adult Wistar rats of either sex received an injection of 50 microL of 5% v/v subcutaneous formalin injection into one vibrissal pad and consequent facial grooming behavior was monitored. Animals exhibited two distinct periods of nocifensive grooming: (a) an acute phase lasting 0-6 min; and (b) a tonic phase lasting 6-45 min. The analgesic response of curcumin was observed at doses of 25, 50, 100, 200, 400 and 600 mg/kg i.p., administered 15 min prior to formalin injection. Another group received subanalgesic dose of diclofenac (0.2 mg/kg) and curcumin 25 mg/kg. Curcumin and diclofenac were administered 15 and 5 min prior to formalin injection respectively. Curcumin produced a dose-dependent inhibition of facial grooming in both acute and tonic phases compared to vehicle and potentiated the subanalgesic dose of diclofenac. The study results for the first time demonstrated the per se antinocifensive effect of curcumin and also exhibited a synergistic interaction with the subanalgesic dose of an NSAID in the facial pain model. More studies are necessary to elucidate the mechanisms of curcumin in this model of pain.

Topics: Analgesics; Animals; Anti-Inflammatory Agents, Non-Steroidal; Curcumin; Diclofenac; Dose-Response Relationship, Drug; Facial Pain; Female; Formaldehyde; Grooming; Male; Pain Measurement; Rats; Rats, Wistar